1. Field of the Invention
The present disclosure relates to a light emitting device and method for producing a light emitting device.
2. Description of the Related Art
In a light emitting device using a semiconductor light emitting element, a flip-chip mounting, in which electric power is applied (power feeding) to a semiconductor light emitting element without using a wire, is known to be employed. For example, in the case of a GaN-system semiconductor light emitting element in which a nitride semiconductor layer is grown on an insulating sapphire substrate, therein a known method in which a p-electrode and an n-electrode are disposed on the respective semiconductor layers (same plane side), then, the electrodes are placed facing the wiring disposed on a circuit substrate and are bonded to the circuit by using an electrically conductive bonding member to establish electrical continuity. With this method, little of the light from the semiconductor light emitting element is allowed to propagate in the substrate direction, so that the light can be released efficiently from the upper surface and side surfaces directions.
Examples of electrically conductive bonding members for establishing electrical continuity between the substrate and the semiconductor light emitting element include solder bumps and plating bumps, but in the case of a small-size light emitting element, due to a short distance between the p-electrode and the n-electrode, a short circuit tends to occur. Thus, an anisotropic conductive adhesive is used as a bonding member. An anisotropic conductive adhesive is made of electrically conductive particles mixed in a thermosetting resin and a film state (ACF: Anisotropic Conductive Film), and a paste state (ACP: Anisotropic Conductive Paste) are known. In the case where an anisotropic conductive adhesive is applied particularly to a microscopic region, ACP is suitable because it can be disposed with any desired size and position by way of printing. For the electrically conductive particles, metal particles or composite particles obtained by coating the surface of insulating particles with a wiring conductor are used, and in the case where the electrically conductive particles are used for the bonding member of the semiconductor light emitting element, conductive particles having high reflectance are known to be used (for example, see Japanese Patent Publication No. 2007-157940 A).
The anisotropic conductive adhesive not only serves to establish electrical continuity but also functions as a die-bonding member for fixing the semiconductor light emitting element, thus, the anisotropic conductive adhesive is disposed with a larger area than that of the semiconductor light emitting element. Also, the anisotropic conductive adhesive is needed to be disposed with a certain thickness, which may lead to a formation of a fillet which covers at least a part of a side surface of the semiconductor light emitting element. However, in order to obtain uniform electric conductivity, the electrically conductive particles are needed to be uniformly dispersed in an anisotropic conductive adhesive with a certain concentration. Accordingly, many electrically conductive particles present in portions surrounding the semiconductor light emitting element in top view and in the fillet. At least the surfaces of the electrically conductive particles are made of a metal which may result in absorption of some of light emitted from the side surfaces of the semiconductor light emitting element.